This invention relates to semiconductor devices, and in particular, to providing ohmic contacts to indium-containing devices.
Semiconductor devices which operate in the long-wavelength region of 1.0 to 1.7 .mu.m are gaining increasing importance in the optical communication field due to their capacity for transmitting and receiving at high bit rates over long distances. Indium-containing devices, such as FETs, LEDs, and photodetectors based on the InP/InGaAsP materials, appear particularly promising for future systems. One problem which exists, however, is providing reliable ohmic contact to the device. For example, typical alloy contacts to the n-type InP substrates include multi-layers of gold and a suitable dopant such as tin (see, e.g., Keramidas et al, "Ohmic Contacts to InP and InGaAsP", Inst. Phys. Conf. Ser., Vol. 56, p. 293 (1981)). Indium has a strong tendency to diffuse into the contact metals and either react with the top gold layer or oxidize. In either case, wire bonding to the surface of such contacts is difficult, resulting in yield and reliability problems.
It is therefore a primary object of the invention to provide a metallization for contacting indium-containing devices so that bonding to the contact is not impeded.